/*
 * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
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 *
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 *
 *
 *
 *
 */
package javax.swing;

import java.awt.FocusTraversalPolicy;
import java.awt.Component;
import java.awt.Container;
import java.awt.Window;
import java.util.HashMap;
import java.util.HashSet;
import java.io.*;


/**
 * A FocusTraversalPolicy which provides support for legacy applications which
 * handle focus traversal via JComponent.setNextFocusableComponent or by
 * installing a custom DefaultFocusManager. If a specific traversal has not
 * been hard coded, then that traversal is provided either by the custom
 * DefaultFocusManager, or by a wrapped FocusTraversalPolicy instance.
 *
 * @author David Mendenhall
 */
final class LegacyGlueFocusTraversalPolicy extends FocusTraversalPolicy
    implements Serializable {

  private transient FocusTraversalPolicy delegatePolicy;
  private transient DefaultFocusManager delegateManager;

  private HashMap<Component, Component> forwardMap = new HashMap<Component, Component>(),
      backwardMap = new HashMap<Component, Component>();

  LegacyGlueFocusTraversalPolicy(FocusTraversalPolicy delegatePolicy) {
    this.delegatePolicy = delegatePolicy;
  }

  LegacyGlueFocusTraversalPolicy(DefaultFocusManager delegateManager) {
    this.delegateManager = delegateManager;
  }

  void setNextFocusableComponent(Component left, Component right) {
    forwardMap.put(left, right);
    backwardMap.put(right, left);
  }

  void unsetNextFocusableComponent(Component left, Component right) {
    forwardMap.remove(left);
    backwardMap.remove(right);
  }

  public Component getComponentAfter(Container focusCycleRoot,
      Component aComponent) {
    Component hardCoded = aComponent, prevHardCoded;
    HashSet<Component> sanity = new HashSet<Component>();

    do {
      prevHardCoded = hardCoded;
      hardCoded = forwardMap.get(hardCoded);
      if (hardCoded == null) {
        if (delegatePolicy != null &&
            prevHardCoded.isFocusCycleRoot(focusCycleRoot)) {
          return delegatePolicy.getComponentAfter(focusCycleRoot,
              prevHardCoded);
        } else if (delegateManager != null) {
          return delegateManager.
              getComponentAfter(focusCycleRoot, aComponent);
        } else {
          return null;
        }
      }
      if (sanity.contains(hardCoded)) {
        // cycle detected; bail
        return null;
      }
      sanity.add(hardCoded);
    } while (!accept(hardCoded));

    return hardCoded;
  }

  public Component getComponentBefore(Container focusCycleRoot,
      Component aComponent) {
    Component hardCoded = aComponent, prevHardCoded;
    HashSet<Component> sanity = new HashSet<Component>();

    do {
      prevHardCoded = hardCoded;
      hardCoded = backwardMap.get(hardCoded);
      if (hardCoded == null) {
        if (delegatePolicy != null &&
            prevHardCoded.isFocusCycleRoot(focusCycleRoot)) {
          return delegatePolicy.getComponentBefore(focusCycleRoot,
              prevHardCoded);
        } else if (delegateManager != null) {
          return delegateManager.
              getComponentBefore(focusCycleRoot, aComponent);
        } else {
          return null;
        }
      }
      if (sanity.contains(hardCoded)) {
        // cycle detected; bail
        return null;
      }
      sanity.add(hardCoded);
    } while (!accept(hardCoded));

    return hardCoded;
  }

  public Component getFirstComponent(Container focusCycleRoot) {
    if (delegatePolicy != null) {
      return delegatePolicy.getFirstComponent(focusCycleRoot);
    } else if (delegateManager != null) {
      return delegateManager.getFirstComponent(focusCycleRoot);
    } else {
      return null;
    }
  }

  public Component getLastComponent(Container focusCycleRoot) {
    if (delegatePolicy != null) {
      return delegatePolicy.getLastComponent(focusCycleRoot);
    } else if (delegateManager != null) {
      return delegateManager.getLastComponent(focusCycleRoot);
    } else {
      return null;
    }
  }

  public Component getDefaultComponent(Container focusCycleRoot) {
    if (delegatePolicy != null) {
      return delegatePolicy.getDefaultComponent(focusCycleRoot);
    } else {
      return getFirstComponent(focusCycleRoot);
    }
  }

  private boolean accept(Component aComponent) {
    if (!(aComponent.isVisible() && aComponent.isDisplayable() &&
        aComponent.isFocusable() && aComponent.isEnabled())) {
      return false;
    }

    // Verify that the Component is recursively enabled. Disabling a
    // heavyweight Container disables its children, whereas disabling
    // a lightweight Container does not.
    if (!(aComponent instanceof Window)) {
      for (Container enableTest = aComponent.getParent();
          enableTest != null;
          enableTest = enableTest.getParent()) {
        if (!(enableTest.isEnabled() || enableTest.isLightweight())) {
          return false;
        }
        if (enableTest instanceof Window) {
          break;
        }
      }
    }

    return true;
  }

  private void writeObject(ObjectOutputStream out) throws IOException {
    out.defaultWriteObject();

    if (delegatePolicy instanceof Serializable) {
      out.writeObject(delegatePolicy);
    } else {
      out.writeObject(null);
    }

    if (delegateManager instanceof Serializable) {
      out.writeObject(delegateManager);
    } else {
      out.writeObject(null);
    }
  }

  private void readObject(ObjectInputStream in)
      throws IOException, ClassNotFoundException {
    in.defaultReadObject();
    delegatePolicy = (FocusTraversalPolicy) in.readObject();
    delegateManager = (DefaultFocusManager) in.readObject();
  }
}
